It is well known that air pollution is a serious issue worldwide and carbon dioxide released by industrial production and internal combustion engines can lead to significant global climate changes. A significant amount of the pollution and carbon dioxide emissions comes from automobiles and other mechanized vehicles such as airplanes, ships, and diesel trucks, which continue to proliferate. Furnaces, boilers and gasifiers using combustion to generate power is another source of pollution and carbon dioxide emissions.
Most of these internal combustion engines, furnaces, boilers and gasifiers run on petroleum-based fuels, such as gasoline, jet fuel, diesel fuel, fuel oil, heating oil and bunker oil. When such fuels are burned, not all of the energy is used and some of the energy is transferred as heat and is lost through the engine (or furnace) surface and the hot exhaust. This exhaust comprises a variety of gases and particulates such as carbon dioxide (CO2), carbon monoxide (CO), nitrous oxides (NOx), sulfur dioxides (SOx), unburned hydrocarbons and soot particulates. All of these are pollutants and each has negative environmental consequences.
In addition, the low boiling point components of gasoline can evaporate when exposed to heat. This evaporation is one of the sources of Haxardous Air Pollutants (HAPs) and volatile organic compounds (VOCs). VOCs and HAPs are toxic to humans and can produce ozone, which is a component of smog as well as a layer in the atmosphere that traps heat.
One potential solution that addresses both the issue of oil scarcity and environmental effects of burning petroleum-based fuels or coal-based fuels is alcohol-based fuels. Several alcohol-based fuels have been proposed in the past, such as methanol and ethanol. Furthermore, hazardous additives such as lead and methyl tert-butyl ether (MTBE) in gasoline can also cause health hazard. The present solution has been to replace these hazardous additives with methanol and ethanol. However, as explained below, there are a number of disadvantages of using ethanol, methanol or other lower alcohols as fuel additives or fuels.
Typically, ethanol is fermented from food crops, primarily grains such as corn, wheat, barley, oats and a variety of other farm grown commodities, often called “biomass.” While ethanol is promoted as a clean, green fuel since the base feedstock is renewable, it has not been a panacea for solving the environmental issues and the oil scarcity issues because a significant amount of energy and fertilizer are needed to produce the feedstock and the ethanol.
Alcohols produced from food as a feedstock are expensive and subject to weather conditions and fluctuations in harvests as well as government regulations. For example, the Chinese government does not allow the use of a food product as a feedstock for producing fuels.
Ethanol can be blended into gasoline at a rate of roughly 7% to 10%. Recent fuel testing at higher levels have shown that engines that are not specifically set up to use ethanol have more wear on the parts leading to a reduction in engine life. Other blends such as E-85, which is 85% ethanol and 15% gasoline, can only be used in engines specifically designed and built to use that fuel blend. Only a very small proportion of the total number of automobiles built are able to use E-85.
Methanol blends such as M-85 (85% methanol and 15% gasoline) are even more problematic. Methanol does not dissolve in gasoline in all proportions. The solubility of methanol in gasoline is a function of both the composition of the mixture and temperature but, in general, mixtures having a methanol content between 15% and 85% tend to separate into two phases. While flexible fuel vehicles can tolerate phase separation in the vehicle fuel tank, it does create a problem in the distribution system as there is no easy way to control the quality of the fuel being dispensed.
Water is vey soluble in methanol and ethanol. Therefore, ethanol or methanol blended fuels, at higher alcohol percentages by volume, have greater propensity to absorb a large amount of water or even exhibit phase separation, which may cause problems in the distribution system of vehicles and pipelines. Consequently, this limits the level of ethanol or methanol that can be safely blended and transported through pipelines.
Methanol can corrode the metal components and wears down the elastomeric components of conventional vehicle fuel systems. One solution to this problem is a redesigned engine using stainless steel and methanol resistant elastomers, but this adds cost to vehicle production. Furthermore, methanol vehicles require special engine oil and larger fuel tanks for having to carry more fuel due to its lower specific heating value and lower energy density than those of gasoline.
Another problem for both ethanol and methanol is that they have a high oxygen content and therefore have lower energy densities than other fuel components. The energy density of methanol and ethanol are respectively 57,000 and 76,000 British Thermal Units (Btus) per gallon, both of which are much lower than gasoline ˜114,500 Btus per gallon. Due to this lower energy content, more ethanol and methanol fuel is needed to achieve the same energy level, translating into a loss of mileage in the case of automobiles or trucks, or a higher consumption of fuel in the case of furnaces.
As for diesel blending, methanol, due to its highly polar nature, is not soluble in diesel fuel and ethanol is only soluble in diesel fuel if it contains very little water. Even if ethanol and methanol could be blended into diesel fuel, their low cetane levels would reduce the cetane level of the diesel fuel to a point where the cetane rating will likely decrease below the level recommended by the engine manufacturer, preventing operation. Further, ethanol does not provide lubrication for the fuel injection system, which is another problem with blending ethanol into diesel fuel. Another problem of these alcohols is the vapor pressure. Methanol and ethanol are too volatile to meet the requirements necessary for diesel fuel to operate as they tend to vaporize in the fuel mixture.
As a result, there are needs for environmental friendly fuel additives to replace the current fuel additives such as MTBE, ethanol and methanol. There are also needs for environmental friendly higher alcohol-based fuels to replace the petroleum-based fuels or the lower alcohol-based fuels. There are also needs for alcohol-based fuels that are not produced from food as a feedstock. There are also needs for alcohol-based fuels that can reduce wear of the engine, the fuel injection system and elastomeric components. There are also needs for alcohol-based fuels that can be blended with gasoline or other petroleum-based fuels with little or no phase separation. There are also needs for higher alcohol-based fuels that have higher energy densities than those of lower alcohol-based fuels.